(a) Field of the Invention
This invention is related to a method of affixing a heat sink to a substrate and package of the heat sink and the substrate, wherein a chip is first affixed to a substrate and then covered with a heat sink for dissipating heat generated during the working of the chip.
(b) Description of the Prior Art
As far as we know, semiconductor chips will generally heat up while working. Therefore, it is necessary to use a heat sink to cover the chip in order to dissipate the heat generated by the semiconductor chip.
The conventional method of affixing and adhering a heat sink to a substrate is shown in FIGS. 1, 2A, 2B and 2C. As illustrated, a semiconductor chip 2xe2x80x2 is first affixed on the substrate 1xe2x80x2, and then a sprayer 4xe2x80x2 is used to apply an adhesive agent 41xe2x80x2 on the substrate 1xe2x80x2 corresponding to the four dimples 31xe2x80x2 on the bottom side of the heat sink 3xe2x80x2. Then the heat sink 3xe2x80x2 is adjusted so that the dimples 31xe2x80x2 are aligned with the adhesive agent 41xe2x80x2 and moved to connect with the substrate. Finally, epoxy resin 5xe2x80x2 is used to enclose the heat sink 3xe2x80x2 to form a package.
However, such a method suffers from the following drawbacks: Firstly, since it is necessary to use the sprayer 4xe2x80x2 to spray an appropriate amount of adhesive agent 41xe2x80x2 to four positions corresponding to the dimples 31xe2x80x2 of the heat sink 3xe2x80x2, the physical and chemical properties of the adhesive agent 41xe2x80x2 within the sprayer 4xe2x80x2 and the decrease in the amount of the adhesive agent 41xe2x80x2 will often change its viscosity, thereby causing the output of the adhesive agent being sprayed to vary. If less adhesive agent 41xe2x80x2 is applied to the substrate, then the heat sink 3xe2x80x2 cannot be firmly attached to the substrate, and so the heat sink will detach from the substrate after further treatment. If the adhesive agent is excessive, the electrical connection between the semiconductor chip and the substrate will be affected and may even be severed.
If the adhesive agent 41xe2x80x2 is not applied to the correct position or the thickness of the adhesive agent 41xe2x80x2 changes, the heat sink will not be firmly attached to the substrate, and may even cause the position of the heat sink to change.
In addition, it is necessary to apply the adhesive agent point by point, and the sprayer 4xe2x80x2 must be positioned and cleaned again for each different package, thereby decreasing the manufacturing efficiency.
Therefore, it is an object of the present invention to provide a method which can obviate and mitigate the above-mentioned drawbacks.
This invention is related to a method of affixing a heat sink to a substrate and package of the heat sink and the substrate, wherein a chip is first affixed to a substrate and then covered with a heat sink for dissipating heat generated during the working of the chip.
It is the primary object of the present invention to provide a method of affixing a heat sink to a substrate which utilizes screen printing technology to apply a layer of adhesive agent with an appropriate thickness of adhesive on a platform from the adhesive agent thereby ensuring the heat sink to be affixed firmly on the substrate.
It is another object of the present invention to provide a method of affixing a heat sink to a substrate which can easily control the thickness of the layer of adhesive agent.
It is a further object of the present invention to provide a method of affixing a heat sink to a substrate which does not require the procedure of positioning and cleaning the nozzle.
According to a preferred embodiment of the present invention, a method of affixing a heat sink to a substrate and package thereof having a substrate with a position for receiving a semiconductor chip, at least a semiconductor chip for affixing on the position and electrically connecting the substrate, an appropriate thickness of adhesive agent by scraping by means of screen printing technology, a heat sink for covering the semiconductor chip and provided with a plurality of dimples for affixing to the substrate, the method comprising steps of affixing the semiconductor to the substrate and utilizing a scraper to apply a layer of adhesive agent with an appropriate thickness of adhesive on a platform from the adhesive agent; utilizing a sucker to move the heat sink to a position above the layer of adhesive agent, and dipping the dimples of the heat sink into the adhesive layer so as to adhere some adhesive agent onto the dimples, and then moving the heat sink above the semiconductor chip; affixing the heat sink to the substrate to cover the semiconductor chip; and enclosing the heat sink with epoxy resin to form a package.
The foregoing object and summary provide only a brief introduction to the present invention. To fully appreciate these and other objects of the present invention as well as the invention itself, all of which will become apparent to those skilled in the art, the following detailed description of the invention and the claims should be read in conjunction with the accompanying drawings. Throughout the specification and drawings identical reference numerals refer to identical or similar parts.
Many other advantages and features of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying sheets of drawings in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example.